Question about 1999 GMC Suburban

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All of a sudden, engine misses badly, poor idle, low fuel economy, strong exhaust smell.

My suburban, 1999 7.4L K2500, started running poorly on a road trip. It won't idle, misses badly, etc. It runs better at high RPM and finished the road trip but used much more gas and when I stop, I need to keep the rpm's up with one foot on the brake and one on the gas. I also smelled a burnt rubber like smell from the passenger side of the engine. All wires and boots appear in good shape. Replaced fuel filter (which was pretty clogged). The only code set was system too rich bank 2. One mechanic said the timing chain skipped but couldn't verify so I took to another who said one cylinder had no compression and I need a new engine! This is the same mechanic that punctured my tire while driving into the shop and didn't want to replace it so I'm not sure how accurate they are. I drove home 600 miles the next day and have been driving off and on since. Has decent (but not great) power just doesn't idle well.
Two other things that may be of interest:
1. The tail pipe was bent a little (about 3") when backing up a steep drive. Bent back with no improvement.
2. I found a downstream O2 sensor on the passenger side that had the wire sheath damaged. It is on top of the tranny so I can't see if the actual wires are damaged.
I was going to drop the oil pan and check for pieces of push rod or something in there but couldn't get the pan out without a lot of trouble. Can this be an exhaust/o2 problem?
Thank you very much!

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I was having this same problem with my '02 Kia Spectra. It would run while driving, but would not idle unless I kept my foot on the gas. It took a while to figure out, and alot of money, but the problem ended up being the MAS (Mass Airflow Sensor). It is located around the air filter. It detects how much air is coming into the motor and is used to determine what ratio to mix the air and gas. I bought an $8 can of Mass Airflow Sensor cleaner and sprayed the heck out of it. Once I put the sensor back on, it was immediately fixed. It took all of 20 minutes to fix. Hope this helps.

Posted on Jan 29, 2009

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I have a 97 sub i would replace the distributor as the gear are soft and go out after 100 k .
i have read a lot on the web with your same problem and all have done the replacement and fixed it .
it also said that if the distributor is off by a hair it will run rough. good luck.

Posted on Nov 04, 2008

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Hello it could be one of a couple of sounds like oxegen sensors or knock senors and last mass air flo senor

Posted on Oct 29, 2008

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